Consider The AFUE Rating When You’re Selecting A High-Efficiency Furnace, But Consider Other Features, As Well

December 22, 2011
By
Steve Guasco

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When selecting a high-efficiency furnace for your home, the annual fuel utilization efficiency (AFUE) rating is an excellent comparison tool. As an example, many older heating systems have an AFUE of somewhere between 68 and 72 percent — which is very low by today’s standards. This rating tells you just how efficiently a furnace or boiler uses energy over a typical winter season.

In addition to AFUE, look for certain physical features in your new system that will add to your energy savings:

Medium-efficiency furnaces (defined as having an AFUE rating of between 80 and 83 percent): These heating systems are most effective when equipped with an exhaust fan controlling the airflow and combustion gases. Lightweight, with a space-saving design that lowers cycling losses. Also look for a small-circumference flue pipe and electronic ignition, which eliminates the need for a pilot light.

High efficiency furnaces (defined as having an AFUE rating of between 90 and 97 percent): A second heat exchanger condenses flue gases, which produces the high level of operating efficiency. A sealed combustion chamber is another energy-saving feature you’ll find in this category. The units have a higher purchase price, but that can be recouped through lower energy bills. Federal tax credits are available for certain models until the end of December.

Older units, like those in many homes here in Oregon, typically have heavy heat-exchange equipment. Combustion gases in many of these units are allowed to flow in an uncontrolled way with natural drafts and they usually have a continuous pilot light.

About electric-fueled boilers or furnaces: these highly-efficient systems have an AFUE rating of 95 percent and above — some are 100 percent efficient. However, the relatively high price of electricity generally makes electric models impractical. For a viable electric option, consider a heat pump, which will lower the energy costs, if installed correctly and maintained regularly.

Talk to your local home heating and cooling experts at Roth Heating & Cooling, Plumbing & Electrical to learn more about furnace efficiency and other HVAC issues. We’re experienced with the latest technology and all major brands.